Tyrosyl phosphorylation regulates human cellular processes from cell differentiation to growth and apoptosis etc. Tyrosyl phosphorylation is regulated by protein-tyrosine kinases (PTK) and protein-tyrosine phosphatases (PTP). The imbalance of regulation governed by PTK and PTP activity leads to various diseases.
SHP2 is a non-receptor protein tyrosine phosphatase (PTP) encoded by the Protein-tyrosine phosphatase non-receptor type 11 (PTPN11) gene. It contains two N-terminal Src homology 2 domains (N—SH2 and C—SH2), a catalytic domain, and a C-terminal tail. The protein exists in an inactive, auto-inhibited basal conformation that blocks the active site. This self-inhibition state is stabilized by a binding network involving residues from both the N—SH2 and catalytic domains. Stimulation by, for example, cytokines or growth factors results in enzymatic activation of SHP2 and makes the active site available for dephosphorylation of PTPN11 substrates.
SHP2 is widely expressed in most tissues and contributes to various cellular functions including proliferation, differentiation, cell cycle maintenance and migration. It is involved in signaling through the Ras-mitogen-activated protein kinase, the JAK-STAT, EGFR, or the phosphoinositol 3-kinase-AKT pathways.
Mutations in the PTPN11 gene and subsequently in SHP2 lead to hyperactivation of SHP2 catalytic activity, and have been identified in several human diseases, such as Noonan Syndrome, Leopard Syndrome, juvenile myelomonocytic leukemias, neuroblastoma, melanoma, acute myeloid leukemia and cancers of the breast, lung, melanoma, neuroblastoma, hepatocellular carcinoma, and colon. These mutations disrupt the auto-inhibition between the N—SH2 domains and the catalytic site allowing constitutive access of substrates to the catalytic site of the enzyme.
Additionally, there is growing evidence that PTPN11/SHP2 may be implicated in immune evasion during tumorigenesis, and hence a SHP2 inhibitor could stimulate the immune response in cancer patients.
Furthermore, SHP2 plays an important role in JAK/STAT3 pathway, with clear correlation between its phosphatase activity and systemic autoimmunity, thus a SHP2 inhibitor could be used to treat autoimmune diseases such as Lupus and Rheumatoid Arthritis.
Therefore, SHP2 represents a highly attractive target for the development of novel therapies for the treatment of various diseases associated with the aberrant activity of SHP2. The compounds of the present disclosure that are capable of inhibiting the activity of SHP2, possess great potential as novel small molecule therapies for the treatment of various diseases mentioned above.